Phase-Bridged Hierarchical Catalysts for Efficient and Stable Water Electrolysis

Abstract

The design and synthesis of low-cost electrocatalysts with high catalytic activity and long-term stability is a challenging task. This study utilizes a combination of electronic tuning and surface reconstruction to synthesize a ternary layered double hydroxide (LDH)/phosphide (P-NiCuFe-LDH) hierarchical-structure catalyst that improves the kinetics of the hydrogen/oxygen evolution reactions in water electrolysis by facilitating the thermodynamically limited reaction pathways. Spectroscopic analyses indicate synergistic electronic interactions among the metal atoms in the LDH and phosphide layers via the P-bridge effect. This cross-layer interaction optimizes the electron transport pathways and reaction kinetics, enabling the proposed hierarchical electrocatalyst to exhibit high intrinsic activity. Theoretical calculations confirm the configuration of the cross-phase bridges and elucidate the origin of the enhanced electrocatalytic effect of P-NiCuFe-LDH. For overall water splitting, the P-NiCuFe0.06-LDH || P-NiCuFe0.06-LDH system requires only 1.517 V to attain a current density of 10 mA cm-2. The P-O-containing surface (generated in situ during water electrolysis) prevents metal-ion leaching and endows P-NiCuFe-LDH with excellent operational stability; as demonstrated by the continuous long-term stability test over 1000 h with negligible performance degradation. This study provides important insights into the design of rational hierarchical structures for a wide range of applications beyond water splitting. A well-designed hierarchical catalyst, P-NiCuFe-LDH, is constructed by structural transformation and surface reconstruction, which enhance the electron transport efficacy and reaction kinetics due to the synergistic electronic interactions via the P-bridge effect. The excellent overall water splitting performance with a low cell voltage of 1.517 V at 10 mA cm-2 is shown by the proposed catalyst, along with remarkable operational stability over 1000 h.image